Kelly Osbourne Says She's Gained Nearly 30 Pounds After Grief-Fueled Weight Loss

Kelly Osbourne is opening up about her dramatic weight loss following the death of her father, Ozzy Osbourne ... revealing she's since gained nearly 30 pounds after grief left her barely able to eat.

The reality star told The Sun she was shocked when she saw photos of herself at the BRIT Awards in February ... admitting she had no idea how thin she'd gotten.

"I couldn't f***ing believe it," Kelly said ... adding she's gained 28 pounds in the six months since.

Kelly insists she wasn't battling an eating disorder ... explaining her grief was so overwhelming that eating made her physically sick.

At one point, she even visited Ozzy's grave with a candle, begging her late father to help her get better. The next day, her mom, Sharon Osbourne, introduced her to therapist Chris Miller ... whom Kelly credits with saving her life.

As TMZ previously reported, Kelly has faced intense scrutiny over her appearance, repeatedly firing back at critics who've commented on her weight.

And she's making some big life changes ... moving from Los Angeles to the English countryside with her 3-year-old son, Sidney, following her split from fiancé Sid Wilson.

Kelly says she wants her son to have a stable childhood without worrying about school shootings ... and she's even joined his school's PTA.